/*
* ECDH helper functions - KPP wrappings
*
* Copyright (C) 2017 Intel Corporation
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation;
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT OF THIRD PARTY RIGHTS.
* IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) AND AUTHOR(S) BE LIABLE FOR ANY
* CLAIM, OR ANY SPECIAL INDIRECT OR CONSEQUENTIAL DAMAGES, OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*
* ALL LIABILITY, INCLUDING LIABILITY FOR INFRINGEMENT OF ANY PATENTS,
* COPYRIGHTS, TRADEMARKS OR OTHER RIGHTS, RELATING TO USE OF THIS
* SOFTWARE IS DISCLAIMED.
*/
#include "ecdh_helper.h"
#include <linux/scatterlist.h>
#include <crypto/ecdh.h>
struct ecdh_completion {
struct completion completion;
int err;
};
static void ecdh_complete(struct crypto_async_request *req, int err)
{
struct ecdh_completion *res = req->data;
if (err == -EINPROGRESS)
return;
res->err = err;
complete(&res->completion);
}
static inline void swap_digits(u64 *in, u64 *out, unsigned int ndigits)
{
int i;
for (i = 0; i < ndigits; i++)
out[i] = __swab64(in[ndigits - 1 - i]);
}
/* compute_ecdh_secret() - function assumes that the private key was
* already set.
* @tfm: KPP tfm handle allocated with crypto_alloc_kpp().
* @public_key: pair's ecc public key.
* secret: memory where the ecdh computed shared secret will be saved.
*
* Return: zero on success; error code in case of error.
*/
int compute_ecdh_secret(struct crypto_kpp *tfm, const u8 public_key[64],
u8 secret[32])
{
struct kpp_request *req;
u8 *tmp;
struct ecdh_completion result;
struct scatterlist src, dst;
int err;
tmp = kmalloc(64, GFP_KERNEL);
if (!tmp)
return -ENOMEM;
req = kpp_request_alloc(tfm, GFP_KERNEL);
if (!req) {
err = -ENOMEM;
goto free_tmp;
}
init_completion(&result.completion);
swap_digits((u64 *)public_key, (u64 *)tmp, 4); /* x */
swap_digits((u64 *)&public_key[32], (u64 *)&tmp[32], 4); /* y */
sg_init_one(&src, tmp, 64);
sg_init_one(&dst, secret, 32);
kpp_request_set_input(req, &src, 64);
kpp_request_set_output(req, &dst, 32);
kpp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
ecdh_complete, &result);
err = crypto_kpp_compute_shared_secret(req);
if (err == -EINPROGRESS) {
wait_for_completion(&result.completion);
err = result.err;
}
if (err < 0) {
pr_err("alg: ecdh: compute shared secret failed. err %d\n",
err);
goto free_all;
}
swap_digits((u64 *)secret, (u64 *)tmp, 4);
memcpy(secret, tmp, 32);
free_all:
kpp_request_free(req);
free_tmp:
kzfree(tmp);
return err;
}
/* set_ecdh_privkey() - set or generate ecc private key.
*
* Function generates an ecc private key in the crypto subsystem when receiving
* a NULL private key or sets the received key when not NULL.
*
* @tfm: KPP tfm handle allocated with crypto_alloc_kpp().
* @private_key: user's ecc private key. When not NULL, the key is expected
* in little endian format.
*
* Return: zero on success; error code in case of error.
*/
int set_ecdh_privkey(struct crypto_kpp *tfm, const u8 private_key[32])
{
u8 *buf, *tmp = NULL;
unsigned int buf_len;
int err;
struct ecdh p = {0};
p.curve_id = ECC_CURVE_NIST_P256;
if (private_key) {
tmp = kmalloc(32, GFP_KERNEL);
if (!tmp)
return -ENOMEM;
swap_digits((u64 *)private_key, (u64 *)tmp, 4);
p.key = tmp;
p.key_size = 32;
}
buf_len = crypto_ecdh_key_len(&p);
buf = kmalloc(buf_len, GFP_KERNEL);
if (!buf) {
err = -ENOMEM;
goto free_tmp;
}
err = crypto_ecdh_encode_key(buf, buf_len, &p);
if (err)
goto free_all;
err = crypto_kpp_set_secret(tfm, buf, buf_len);
/* fall through */
free_all:
kzfree(buf);
free_tmp:
kzfree(tmp);
return err;
}
/* generate_ecdh_public_key() - function assumes that the private key was
* already set.
*
* @tfm: KPP tfm handle allocated with crypto_alloc_kpp().
* @public_key: memory where the computed ecc public key will be saved.
*
* Return: zero on success; error code in case of error.
*/
int generate_ecdh_public_key(struct crypto_kpp *tfm, u8 public_key[64])
{
struct kpp_request *req;
u8 *tmp;
struct ecdh_completion result;
struct scatterlist dst;
int err;
tmp = kmalloc(64, GFP_KERNEL);
if (!tmp)
return -ENOMEM;
req = kpp_request_alloc(tfm, GFP_KERNEL);
if (!req) {
err = -ENOMEM;
goto free_tmp;
}
init_completion(&result.completion);
sg_init_one(&dst, tmp, 64);
kpp_request_set_input(req, NULL, 0);
kpp_request_set_output(req, &dst, 64);
kpp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
ecdh_complete, &result);
err = crypto_kpp_generate_public_key(req);
if (err == -EINPROGRESS) {
wait_for_completion(&result.completion);
err = result.err;
}
if (err < 0)
goto free_all;
/* The public key is handed back in little endian as expected by
* the Security Manager Protocol.
*/
swap_digits((u64 *)tmp, (u64 *)public_key, 4); /* x */
swap_digits((u64 *)&tmp[32], (u64 *)&public_key[32], 4); /* y */
free_all:
kpp_request_free(req);
free_tmp:
kfree(tmp);
return err;
}
/* generate_ecdh_keys() - generate ecc key pair.
*
* @tfm: KPP tfm handle allocated with crypto_alloc_kpp().
* @public_key: memory where the computed ecc public key will be saved.
*
* Return: zero on success; error code in case of error.
*/
int generate_ecdh_keys(struct crypto_kpp *tfm, u8 public_key[64])
{
int err;
err = set_ecdh_privkey(tfm, NULL);
if (err)
return err;
return generate_ecdh_public_key(tfm, public_key);
}
